When we say "double time for Sunday," we can compute the pay by multiplying the pay by 2 and using the given hours, or we can multiply the hours by 2 and use the given pay. It may be easier to do the latter.
... (38 h + 2×8 h) × ($15.50/h) = 54×$15.50 = $837
Wind Song's gross pay for the week will be $837.00.